The Internet enables access to resources, such as video or audio files, web pages for particular subjects, book articles, or news articles. A search system can identify resources in response to a search query that includes one or more search terms or phrases. The search system ranks the resources based on their relevance to the search query and resource importance to provide search results that reference the identified resources. The search results are typically ordered according to a rank score that is assigned to each of the resources based on the relevance of the resource to the search query.
When a search query is unambiguously directed to a particular topic, search results that are closely related to the particular topic can be identified based solely on the terms of the search query. Sometimes, however, the particular topic for which information is being requested may not be clear from the terms of the search query alone. Therefore, search queries can be classified based on the particular topic for which information is being requested.